CA2561263 entitled “Multiple layer roofing underlayment material” discloses a multiple-layered roofing underlayment material comprising an inner core providing a continuous film water barrier, a first outer layer comprising a woven or spun bond fabric and a second outer layer comprising a woven or spun bond fabric, wherein the inner core binds the first outer layer to the second outer layer.
The inner core of the underlayment acts as a binder for the outer layers and provides water resistance through the use of a thermoplastic, resinous, wax, or polymeric material. Numerous material can be used to provide a continuous film water barrier inner core, such as asphalt, polyethylene terephthalate (PET), polyvinyl chloride (PVC), pine pitch, polypropylene, polyethylene, polyamides, polyester, and nylon. In the preferred embodiment, the inner core is a thermoplastic comprising asphalt because of the advantageous features associated with its physical properties, processability, and inexpensive cost. Asphalt's low cost allows for the efficient application of a sufficient film thickness in order to provide for good quality body, or a product that has a heavy canvas feel and adequate stiffness.
An outer layer 120 of the underlayment consists of a spun bond fabric layer. The spun bond fabric layer, when combined with an inner core 110 and a woven fabric outer layer 130, forms a three-layer underlayment material 100. A plurality of outer layers of either non-woven, e.g., spun bond, fabric or woven fabric can be used to produce a multi-layered underlayment material. Because the spun bond layer is not needed to provide strength to the product, it can be very light-weight material, such as 43 grams/m2 or less.
Either a woven fabric or spun bond fabric can be used for the upper and/or the lower layer. One of the layers is preferably woven to ensure that the underlayment has good strength characteristics, and one of the layer is preferably a spun bond or other type of non-woven fabric. When used as a lower layer, the spun bond fabric layer provides good grip to the roof deck. The thermoplastic inner core can be positioned between two or more layers of either woven fabric or spun bond fabric, or any combination thereof.
However, the above multiple-layered roofing underlayment material still has the following drawbacks during practical application.    1. Poor waterproof and leak-resistant properties: Since the multiple-layered underlayment material has a relatively higher thermal shrinkage, when the multiple-layered underlayment material is fixed with nails, the parts of multiple-layered underlayment material around nails intensively shrink after being heated by sunshine, and as a result nails are separated from the multiple-layered underlayment material and circular orifices form around nails and cannot disappear under cooling. Thus water leaking or seepage will consequently occur.    2. Poor environmental protection properties: Since the inner core as mentioned in the background art is preferably asphalt for water-proof and binding, the upper and lower woven or spun bond fabric are bonded by the asphalt to form the roofing underlayment material. However, since the fluidity of asphalt in the multiple-layered roofing underlayment material under heating is not effectively controlled, the asphalt core between the upper and lower woven or spun bond fabric layers will inevitably flow or leak out of the upper and lower woven or spun bond fabric and cause environmental pollution.    3. Poor weathering resistance and peeling strength: the inherit properties of woven fabric lead to a non-affinity binding between the woven fabric and asphalt, such that the core of the multiple-layered roofing underlayment material formed by composite molding is prone to be peeled and separated, and will embrittle and age after being exposed to atmosphere for about 15 days and finally decomposes into powder. Thus, its weathering-resistant property and peeling strength may be poor.    4. Poor stiffness: Since the multiple-layered underlayment material does not contain a net-like reinforcement layer, when a roll of the multiple-layered underlayment material is open under hot weather, the material cannot automatically stretch so that construction efficiency and effect will be affected, and conglutination will inevitably occurs.    5. Light pollution: Since the outer layer of the multiple-layered underlayment material is white polypropylene that reflects sunshine intensively, the light pollution generated thereby is harmful to constructors. In addition, the poor anti-slip property will make the construction unsafe.    6. Poor practical applicability: Since the core of the multiple-layered underlayment material is preferably asphalt, due to the limitation of physical and chemical properties of asphalt, the asphalt layer has lower strength under cold weather and is prone to generate cracks and lose water-proof property; while the asphalt layer between the upper and lower woven or spun bond fabric layers flows out under hot weather because the fluidity of asphalt is not effectively controlled, such that water-proof and leak-resistant function cannot be implemented, at the meantime environment will be polluted.